The Helios prototype (wing span 247 ft.) broke-up in mid-air at an altitude of 2,800 feet under very large wing dihedral deformation (wing tip deflection reaching 40 ft.). Flexible structures, such as the wings on the Helios prototype aircraft, can benefit from a technology for monitoring deformations. In the case of highly flexible aircraft, it can be advantageous to monitor deformations of structures for feedback control and flight safety.